Illumination system for instrument panel display



April 3, 1962 G. K. c. HARDESTY ILLUMINATION SYSTEM FOR INSTRUMENT PANEL DISPLAY 3 Sheets-Sheet 1 Original Filed Sept. 50, 1958 INVENTOR e. K. c. HARDESTY FIG.

ATTORNEYS April 3, 1962 G. K. c. HARDESTY 3,027,669

ILLUMINATION SYSTEM FOR INSTRUMENT PANEL DISPLAY Original Filed Sept. 30, 1958 3 Sheets-Sheet 2 INVENTOR G. K. C. HARDESTY FIG. 3.

,8. 4. ATTORNEYS April 3, 1962 5. K. c. HARDESTY 3,027,659

ILLUMINATION SYSTEM FOR INSTRUMENT PANEL DISPLAY Original Filed Sept. 30, 1958 3 Sheets-Sheet 3 J I 256V INVENTOR G. K. C. HARDESTY ATTORNEYS FIG. 4. BY

3,27,hii9 Patented Apr. 3, i962 lice 3,027,669 ILLUMINATION SYSTEM FOR INSTRUMENT PANEL DISPLAY George K. C. Hardesty, Box 156, Mayo, Md.

Original application Sept. 30, 1958, Ser. No. 764,462, new

Patent No. 2,982,039, dated May 2, 1961. Divided and this application Nov. 30, 1959, Ser. No. 856,312

11 Claims. (Cl. 40-130) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention pertains to the illumination of instrument dials, panels, and plotting boards for shipboard and aircraft as well as other similar purposes.

This case is a division of co-pending application Serial No. 764,462 filed September 30, 1958, now Patent No. 2,982,039.

More particularly, this invention relates to edge lighting in combination with electroluminescent sources and alternate and optional tungsten filament light sources.

Heretofore, edge lighting, that is, panel illumination wherein one or more light sources are located at the edge of a transparent panel and light rays introduced into the panel for transillumination thereof and indirect illumination thereby, has been carried out more or less exclusively by tungsten filament lamps, fluorescent lamps or the like located at the edge of the panel; hence the name edge lighting.

Electroluminescence, on the other hand, has been used only for direct illumination. That is, pointers, indicia or the like are either formed as electroluminescent members or are located directly in front of electroluminescent members for direct illumination thereby.

Electroluminescent light sources have certain inherent advantages over tungsten filament lamps. For example, for panel illumination, 6 volts is a practical maximum that may be used for the miniature lamps required. Tungsten filaments are rich in red light and they emit appreciable light through the several bands of the visible spectrum at this conservative voltage, and such lamps have a relatively long life. However, as tungsten filaments are dimmed, either by design or through age, the other bands of the visible spectrum disappear and substantially only red light is emitted. Electroluminescent light sources, on the other hand, operate most efliciently at around 250 volts. Electroluminescent sources can efliciently emit light rays from orange-yellow through blue, with practically no emission of red rays. The color characteristics of light rays emitted by an electroluminescent source, however, do not appreciably change with dimming.

In various military installations, as described in detail hereinafter, it is highly desirable, if not imperative, that the light source of an illuminated panel be capable of emitting light rays, whether bright or dim, throughout the entire visible spectrum. In an edge-lighted plotting board for example, it is necessary that the range rings, bearing lines and the numerals, which are permanently applied to the reverse side of the transparent panel, be in distinctly different colors, and it is necessary that the temporary plotting markings, whether they be by grease pencils, as shown herein in FIG. 1, pressure-sensitive adhesive tabs, or small suction cups, also be in distinctly different colors, readily distinguishable at a glance from each other and from the permanent markings.

Applicant has discovered that by combining the desirable features of tungsten filament light sources with those of electroluminescent sources a synergistic effect is produced. Applied to a plotting board, for example, light rays from both tungsten filament sources and from electroluminescent sources are introduced into the transparent, light-transmitting panel for transillumination of such panel. The different light sources are so arranged relative to the light-transmitting panel that they may be used separately or in combination. That is, for installations where the tungsten filament source will do the job alone, as where only the red range of the spectrum is needed, only the tungsten source is energized; where the electroluminescent source will do the job alone, as where the blue through orange-yellow range of the spectrum is needed, only the electroluminescent source is energized: and where the entire visible spectrum is required, both the tungsten source and the electroluminescent source are energized. When both sources of light are energized, the transparent panel is transilluminated by a substantially white light, which white light may be separated into its various distinct color components as desired, as pointed out in detail hereinafter.

An object of the present invention is to provide an efficient and practical illuminated panel construction in the nature of an edge-illuminated panel.

A further object of this invention is to provide an illuminated panel utilizing electroluminescent sources for indirect lighting.

A further object of this invention is to provide an illuminating panel combining desirable features of electroluminescent lamps with desirable features of tungsten lamps.

The broad principles of this invention may be applied to edge-lighted plotting boards and to see thru transparent illuminated scales, dials, pointers and the like.

Briefly, this invention facilitates the viewing of nonelectroluminescent indicia and other graphic material made luminous by light given 01f by concealed electroluminescent sources applied to suitable hidden surfaces of a transparent, light-conducting panel and alternatively capable of supplementary or optional illumination from tungsten lamps, or the like, applied in a complementary edge lighting relationship.

By this invention, the utility of electroluminescent lamps in instrument illumination is greatly extended, since it is not necessary that the electroluminescent material itself be viewed. The indicia or markings, for example, may be of suitable, high diffuse reflectivity, opaque or translucent, materials chosen for excellent daylight visibility as well as high apparent luminosity when viewed at night or in dark environments. The applied indicia may be any color or reflectivity paint, fired on composition, or the like, or the Corning Glass Works type of photosensitive graphic technique may be used.

The instant invention may be used with a single panel illumination system and it is compatible with and may be used with the Duo-Panel System Edge Illumination System, illustrated and described in applicants co-pending patent application Serial No. 369,976, filed July 23, 1953, now US. Patent No. 2,886,911.

The present divided invention, together with the above and other objects and advantages thereof, is set forth in more technical detail in the following description when considered in connection with the accompanying drawings wherein like reference numerals designate like parts throughout the several views thereof and wherein:

FIG. 1 is a face view of an illuminating panel construc- -ftion illustrating one embodiment of the present invention or single panel system in the FIG. 4 is a schematic wiring diagram of the lighting system applied to a plotting board.

Referring now to the drawings wherein FIG. 1, the panelboard, designated generally by reference numeral 10, includes a panel or light-transmitting member made of glass or a highly transparent plastic. The light-transmitting panel comprises a relatively fiat highly transparent plate, having its front and back surfaces in parallel relation to each other and preferably polished to provide smooth optical surfaces. The light transmitting member is preferably fabricated from an acrylic resin or methyl methacrylate plastic material of the thermoplastic type such as, for example, commercial Plexiglas or Lucite. The boundary surfaces of the panel, including the major front and back surfaces, are polished for high specular reflectivity.

A laminated border or framework of electroluminescent material, indicated generally by reference numeral 14 in FIG. 2, is placed around the periphery of panel 40. Electroluminescent material, per se, is Well-known in the art and need not be described in detail here. For purpose of illustration, the lamination 14 comprises a layer of electroluminescent material such as phosphor granules embedded in a transparent plastic or glass matrix, and sandwiched between a transparent electrical conductor and an opaque electrical conductor, as set forth in said application Serial No. 764,462. A pair of leads 14e are connected to said conductors and lead to and from a suitable source of AG. current, not shown.

In accordance with the preferred embodiment of the invention illustrated in FIGS. 1-4, the electroluminescent material is used as the only electroluminescent light source. The lamination 14 functions as a frame for the panel and it utilizes a part of the panel that would otherwise be wasted insofar as illumination is concerned; this portion of the panel being generally located within a cabinet or casing.

For see thru panels, so as to prevent disturbing refiections at the front or obverse surface of the panel, a coating of a light-absorbing dye may be incorporated in the rear surface of the light-transmitting panel adjacent the electroluminescent material. The extent of the lightabsorbing dye is dependent upon the use of the panel and, in some applications, the electroluminescent material may be omitted from the rear surface of the light-transmitting panel and in its place such surface may be covered with the light-absorbing dye.

With the arrangement shown in FIGS. l-4, light introduced into the light-transmitting panel 40 from the electroluminescent material is transmitted through the panel by internal reflection in the manner of edge'lighting and such light may be tapped oif as desired. For purpose of illustration, an indicia may be placed in optical contact with the rear surface of the light-transmitting panel, which indicia is thereby rendered luminous and viewable through the panel from the front surface thereof. The indicia may be located on the front or back surface of the panel, as desired, and, since the electroluminescent source of light is itself not viewable, the indicia or other markings may be of suitable, color, high diffuse reflectivity, opaque or translucent, materials chosen for excellent daylight visibility as well as high apparent luminosity when viewed at night or in a dark environment.

In FIGS. 1, 2, 3 and 4 there is illustrated a practical embodiment of the invention applied to an edge-lighted, vertical plotting board PB. As pointed out hereinbefore, FIG. 1 is a front elevational view of the construction of the plotting board PB and FIGS. 2 and 3 are partial vertical sections taken on lines 22 and 33 of FIG. 1, looking in the direction of the arrows. The plotting board PB, known in the art as a 60 inch-vertical plotting board in that it provides a vertical surface sixty inches square for plotting, is not per se applicants invention and is used here as another illustration of the versatility of applicants invention.

Referring now more specifically to FIGS. 1, 2, 3 and 4, the plotting board PB comprises a square light-transmitting panel 40, fabricated of highly transparent plastic, such as an acrylic resin or methyl methacrylate and having its front and back surfaces 40a and 40b parallel and polished to provide smooth optical surfaces. The board is mounted in a square frame or housing, indicated generally by reference numeral 42, comprising front and rear channel members 42a and 42b. A control box 44 is suspended from the lower center portion of the frame. The plotting board is secured to the frame members by a plurality of studs 46 having acorn nuts 48 on opposite ends thereof and with gaskets 50 between the frame members and the front and back surfaces of the light-transmitting panel. The frame with the plotting board mounted therein is supported in a vertical position by suitable supports, not shown.

As shown in FIGS. 2 and 3, and in dotted lines in FIG. 1, each of the four sides of the frame houses six, 6 volt, 3 candle power tungsten lamps, indicated generally by reference numeral 52. The lamps protrude through clearance holes 54, provided in the light-transmitting panel near the edges thereof and within the frame, in order to properly align the lamp filament for optimum edge lighting eifect. The lamps are accessible for replacement by removing a lamp cover plate 56, which cover plate is secured to the rear frame member by a plurality of studs 5%. A chalk tray 60 extends along the bottom of the board at the front and rear thereof.

In accordance with this invention, the light-transmitting panel is provided with an electroluminescent light source along its marginal edges. This light source, indicated by reference numeral 14, is generally similar to that illustrated in FIG. 2 in that it includes an electroluminescent material sandwiched between an inner, current-conducting transparent lamina and an outer, opaque culrent-conducting lamina with a protective coating over the outer lamina. The electroluminescent light source 14 is provided With suitable openings therein for protrusion of the tungsten lamps S2 therethrough, as shown in FIGS. 2 and 3. The frame members are provided with vent openings 64- for circulation of air therethrough so as to dissipate heat thrown off by the light sources.

Referring still to FIGS. 1, 2, 3 and 4, for ship installations, the light-transmitting panel 40 is provided with a cylindrical recess 66 in its front in the upper right hand corner (FIG. 4), in which recess is mounted a circular dial 6%. The surfaces of the cylindrical recess and the surfaces of the dial (FIG. 2) are polished for efiicient transmission of light therethrough, and the dial is flush with the front surface of the panel. The dial, which is fabricated of transparent light-transmitting plastic, is mounted for rotation on a shaft 70, which shaft is rotated by a synchro motor 71. The motor is mounted on the rear frame member by a bracket 72 attached to the frame by a pair of studs 73. As shown, the dial is formed with a cross pointer 74- (FIG. 1) thereon and with graduations around its periphery. The adjacent surface of the panel is provided with like graduations at 15 intervals and marked 000()30060, etc. The purpose of the dial, as will be described hereinafter, is to indicate the ships course; a reference course referred to hereinafter as Own Ships Course or O.S.C. For land installations, the dial may be omitted.

Referring again to the light-transmitting panel 40, and with reference to FIG. 1, the back or reverse surface of panel 40 is formed With polar co-ordinate markings comprising range rings and solid and dashed bearing lines 82a and 82b. The range rings are arranged as concentric circles and are a fixed distance apart. The solid bearing lines are 30 apart and are so marked. The dashed bearing lines interpolate every ten degrees between the solid bearing lines and are so marked. The polar co-ordinate markings including the numerals are applied to the back of the panel by a silk screening process, known in the art. Preferably all range circles, bearing lines and numerals on the back of the principal panel 40 are green in color and are permanent. The bearings, markings and numerals around the circumfen ence of the O.S.C. dial 68 are painted on the back of the principal panel and are orange in color. The bearing lines and the cross pointer for the O.S.C. dial are painted on the back of such dial and are orange in color. All plotting, range, bearing and identification markings are inscribed on the back of the panel, backwards, so that such markings may be read correctly from the front.

The temporary or movable markings, used for plotting, are also applied to the back of the panel and viewed from the front. Three such plotting markings, which may be indicated at X, Y and Z, are shown and may be made by erasable grease pencils, pressure-sensitive adhesive tabs, small vacuum cups, or the like, and because of the substantially white light introduced into the panel by the combination of electroluminescent and tungsten filament light sources, these markings, which are of diffuse material, may be of any color within the visible spectrum.

In FIG. 4 there is shown a schematic wiring diagram for the tungsten lamps, the electroluminescent light source and for the synchro motor. Referring now to FIG. 4 the tungsten filament lamps 52 are connected in parallel by conductors 53 on one circuit and energized by a 115 v./ 7 v. transformer 86. An on-oif snap switch 88 located on the front of 'the central box is provided in the 115 v. circuit energizing the transformer. The illumination intensity of the tungsten lamps is controlled by a variable rheostat 9% located in the control box (FIG. 4). A suitable circuit including conductors 14a is provided for the electroluminescent light source 14. That is, the electroluminescent light source is energized by a special characteristic, 115 v./250 v., transformer 92., having a snap switch 94 and a variable rheostat 96 in the 115 v. transformer circuit.

The circuits shown in FIG. 4 for the plotting board illustrated in FIGS. 1, 2 and 3 may be used with embodiments of the invention such as illustrated in the parent case. That is: when the red end of the range of the visible spectrum is required, only the tungsten source is energized and this source may be dimmed as desired; when the blue-violet end of the range of the visible spectrum is required, only the electroluminescent source is energized and this source may be dimmed as desired; and when the entire range of the visible spectrum is required, both light sources are energized and may be dimmed as desired. Thus, with the instant invention, any or all of the principal colors, red, orange, yellow, green, blue and violet, of the visible spectrum may be taken from the light-transmitting panel and used as desired. Also, these colors may be dimmed without losing their distinctiveness and, in fact, many distinctive shades of the principal colors may be taken from the lighttransmitting panel.

As pointed out hereinbefore, the electroluminescent light source may or may not, as desired, be placed in optical contact with the light-transmitting panel. In certain installations it is desirable that the electroluminescent light source be readily removable from the panel, in which case optical contact would not be provided between the transparent conductor and the adjacent surface of the light-transmitting panel by the mere interface relation of such surfaces. Where desired, certain advantages of optical contact may be attained by providing light diffusing characteristics to the surfaces of the light transmitting panel in those areas that intercept light from the electroluminescent light source. These diffusing characteristics may be provided by roughening the surfaces of the lighttransmitting panel which are adjacent the electroluminescent light source and by applying a diffusing surface to the opposite or light reflecting surface of the light-transmitting panel. Where optical contact is provided light can be regarded as originating under the principal surfaces of the light-transmitting panel and roughening is of less utility.

Having thus described the invention, :it is to be understood that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

What is claimed is:

1. An illumination system comprising a transparent light-transmitting panel having front and rear surfaces arranged for specular reflection of light therebetween and a marginal portion for receiving light, a plurality of indicia on one of said surfaces of said transparent panel, said marginal portion being provided with a plurality of spaced openings therein for receiving light sources, a first source of light energy positioned within each of the openings in the panel for introducing into the panel light energy of a range of wave lengths of the visible spectrum from red through yellow, a second source of light positioned adjacent the marginal face and edge portions of the panel for introducing into the panel light of energy of a range of wave lengths of the visible spectrum from blue-violet through yellow, and means including said first and second light sources and said panel whereby the component waves introduced into the panel are integrated and combined therein thereby producing substantially pure white light containing substantially all of the colors of the visible spectrum and dimming means for said sources of light energy.

2. An illumination system as set forth in claim 1 in which said first source of light energy comprises a tungsten filament lamp.

3. An illumination system as set forth in claim 1 in which said second source of light energy comprises an electroluminescent source.

4. An illumination system as set forth in claim 1 in which said first source of light energy comprises a tungsten filament lamp and said second source of light energy comprises an electroluminescent source.

5. An illumination system comprising a transparent light-transmitting panel having front and rear surfaces arranged for specular reflection of light therebetween and a marginal portion for receiving light, a plurality of indicia on one of said surfaces of said transparent panel, said marginal portion being provided with a plurality of spaced openings therein for receiving light sources, a first source of light energy positioned within each of the openings in the panel for introducing into the panel light energy of a range of wave lengths of the visible spectrum from red through yellow, and a second source of light positioned adjacent the marginal portion of the panel for introducing into the panel light energy of a range of wave lengths of the visible spectrum from blue-violet through yellow, and means including said first and second light sources and said panel whereby the component waves introduced into the panel are integrated and combined therein, thereby producing substantially pure white light containing substantially all colors of the visible spectrum.

6. An illumination system as set forth in claim 5 including means for selectively energizing the first and second light sources, said energizing means comprising a first electric circuit for the first light source having an on-off switch therein for selectively energizing and de-energizing said first source, a second electric circuit for the second light source having an on-oif switch for energizing and de-energizing said second light source, and a rheostat for varying the energy supplied to each light source.

7. An illumination system as set forth in claim 5 in which said first source of light energy comprises a tungsten filament lamp.

8. The combination of claim 7 in which an annular lamp cover plate is detachably secured in spaced relation over the tungsten lamps.

9. An illumination system as set forth in claim 5 in which said second source of light comprises an electroluminescent material.

10. An illumination system as set forth in claim 9 in which the layer of electroluminescent material extends over the peripheral surface and adjacent marginal portions of the light panel transmitting panel.

11. An illumination system as set forth in claim 5 in which said first source of light energy comprises a tungsten filament lamp and in which said second source of light energy comprises an electroluminescent material.

References Cited in the file of this patent UNITED STATES PATENTS wine-.1- mwy- 

